[tip:x86/microcode] x86/microcode/intel: Fix initrd loading with CONFIG_RANDOMIZE_MEMORY=y

[tip-bot for Borislav Petkov <tipbot@zytor.com>]

Commit-ID:  efaad554b4ffae1840a2759e09e21325ddbc8b05
Gitweb:     http://git.kernel.org/tip/efaad554b4ffae1840a2759e09e21325ddbc8b05
Author:     Borislav Petkov <bp@suse.de>
AuthorDate: Tue, 26 Jul 2016 11:51:38 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 26 Jul 2016 19:32:57 +0200

x86/microcode/intel: Fix initrd loading with CONFIG_RANDOMIZE_MEMORY=y

CONFIG_RANDOMIZE_MEMORY=y randomizes the physical memmap and thus the
address where the initrd is located. Therefore, we need to add the
offset KASLR put us to in order to find the initrd again on the AP path.

In the future, we will get rid of the initrd address caching and query
the address on both the BSP and AP paths but that would need more work.

Thanks to Nicolai Stange for the good bisection and debugging work.

Reported-and-tested-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160726095138.3470-1-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/cpu/microcode/intel.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 6515c80..0f97ae9 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -793,10 +793,10 @@ void __init load_ucode_intel_bsp(void)
 void load_ucode_intel_ap(void)
 {
 	struct ucode_blobs *blobs_p;
+	unsigned long *ptrs, start = 0;
 	struct mc_saved_data *mcs;
 	struct ucode_cpu_info uci;
 	enum ucode_state ret;
-	unsigned long *ptrs;
 
 #ifdef CONFIG_X86_32
 	mcs	= (struct mc_saved_data *)__pa_nodebug(&mc_saved_data);
@@ -815,8 +815,20 @@ void load_ucode_intel_ap(void)
 	if (!mcs->num_saved)
 		return;
 
+	if (blobs_p->valid) {
+		start = blobs_p->start;
+
+#ifdef CONFIG_RANDOMIZE_MEMORY
+		/*
+		 * Pay attention to CONFIG_RANDOMIZE_MEMORY=y as it shuffles
+		 * physmem mapping too and there we have the initrd.
+		 */
+		start += PAGE_OFFSET - __PAGE_OFFSET_BASE;
+#endif
+	}
+
 	collect_cpu_info_early(&uci);
-	ret = load_microcode(mcs, ptrs, blobs_p->start, &uci);
+	ret = load_microcode(mcs, ptrs, start, &uci);
 	if (ret != UCODE_OK)
 		return;